Fingerspelling (or dactylology) is the representation of the letters of a writing system, and sometimes numeral systems, using only the hands. These manual alphabets (also known as finger alphabets or hand alphabets), have often been used in deaf education, and have subsequently been adopted as a distinct part of a number of sign languages; there are about forty manual alphabets around the world. Historically, manual alphabets have had a number of additional applications—including use as ciphers, as mnemonics, and in silent religious settings.